The present invention relates to a motor-vehicle door latch. More particularly this invention concerns such a latch with a power-closing feature.
A standard motor-vehicle door latch has a housing normally mounted on a door edge, a fork engageable around a bolt normally carried on a door post and pivotal on the housing from an open position through a partially closed position into a fully closed position, and a latch pawl engageable with the fork in the partially and fully closed positions to retain the fork therein. In a power-closing latch a rocker is provided with a closing pawl that can engage the fork once a sensor reports that the fork is in the partially latched position to push the fork into the fully closed position. Thus the user pushes the door closed so that the partially closed position is assumed, and thereafter the power-closing system pulls the door fully closed. Such a system ensures that the door is very tightly closed without requiring the user to use an untoward effort or slam the door.
In the system described in German patent document 3,836,771 of Deischl the power-closing mechanism is connected to the linkage between the door handle and the latch pawl. In another system described in commonly owned U.S. Pat. No. 5,802,894 an electric motor is used for the power closing and in case of a power failure the latch cannot be operated, in general the systems interfere with standard manual actuation of the latch and often are inordinately complex.
It is therefore an object of the present invention to provide an improved power-closing motor-vehicle door latch.
Another object is the provision of such an improved power-closing motor-vehicle door latch which overcomes the above-given disadvantages, that is which is relatively simple and which allows the door to be opened manually even in the event of a total power failure of the vehicle.
A power-closing motor-vehicle door latch has according to the invention a housing and a fork engageable around a bolt, formed with an abutment, and pivotal on the housing from an open position through a partially closed position into a fully closed position. A latch pawl engageable with the fork in the partially and fully closed positions can retain the fork therein. A rocker is pivotal on the housing between inner and outer positions and a closing pawl is pivoted on the rocker between an entrainment position engageable with the fork abutment and a freeing position unengageable with the fork abutment. A crank drive displaces the rocker outward toward the outer position with the closing pawl in the entrainment position so as to pivot the fork from the partially closed position into the fully closed position and displaces the rocker oppositely inward toward the inner position. A control member is pivotal on the rocker between a pair of end positions. An actuation formation on the control member and an abutment on the housing displace the control member into one of its end positions on displacement of the rocker into the outer end position and displace the control member into the other of its end positions on displacement of the rocker inward into the inner end position. A spring engaged between the control member and the closing pawl urges the closing pawl into the freeing position when the control member is in the one end position and urges the closing pawl into the engaging position when the control member in the other end position.
Thus with this system the power-closing system is only engaged with the lock form when it is moving it from the partially closed to the fully closed position. Otherwise it is disengaged from the fork so that the latch can be operated normally, even if all on-board power has failed.
According to the invention the control member is formed with an arcuate slot and the rocker is provided with a pin engageable with respective ends of the slot in the end positions of the control member. Alternately the rocker could be formed with slot and the pin could be provided on the control member. Either way the slot is made narrow in the center so that the system is metastable, with the pin only resting stably in one end or the other of the slot. The slot and control-member actuation formation are on opposite sides of the control member.
In accordance with the invention the rocker and fork are coaxially pivoted and similarly the control member and closing pawl are coaxially pivoted. Thus the closing pawl will bear angularly on the fork for excellent force transmission.
According to another feature of the invention an actuation formation on the closing pawl and an abutment on the housing retain the closing pawl in the freezing position in the inner position of the rocker. Thus only when the rocker is raised by the drive from its outer position is the spring force able to move the closing pawl into the entrainment position.
The control member and the closing pawl according to the invention are pivoted on a common pivot and are each provided offset therefrom with a respective axially extending pin. The spring can be a torque spring engaged around the pivot and having a pair of arms engageable with the pins. Of course another type of spring, for instance a tension spring hooked on radially offset points on the control member and closing pawl.
The power-closing motor-vehicle door latch wherein the actuator includes two abutments on the housing engageable with the control-member actuation formation in the inner and outer positions of the rocker. Thus when the rocker is retracted to its starting position the control member is flipped to reverse the spring bias so that, when the rocker is pushed forward again to power-close the door, the closing pawl will engage the fork. The housing includes a bearing plate forming one of the housing abutments.
The fork according to the invention is formed with a pair of offset abutments engageable with the latch pawl in the partially and fully closed positions of the fork. It is possible for the same abutment of the fork to be engageable with the latch pawl and with the closing pawl.